The present invention relates to an in-marrow nail structure which has enhanced strength and the breakage taking place at the section where stress is concentrated is avoided. Therefore, a more firmly restoring and fixing effect is provided for the fractured skeleton and the possibility of complications is lowered and the recovering time is shortened and a good curing effect is achieved.
In accidental injury, fracture of clavicle is one of the often seen injury. The existent treatments for fractured skeleton include: 1. Manual osteopathy co-used with sponge 8-bandage or plaster 8-bandage; and 2. Operation osteopathy and internal fixing such as in-marrow nail or steel board for internal fixing. Most of the cases can achieve good effect by way of manual osteopathy and 8-bandage. Only some of the cases necessitate operation treatment. Many fracture patterns or portions can be hardly treated by means of manual osteopathy to achieve a desired fixing effect. This prolongs recovering time. The operation osteopathy is able to achieve a firm fixing effect as well as a complete restoring effect with shortened recovering time. In order to enhance the chance of recovering and reduce the possibility of complications, the compressive in-marrow nail treatment is applied to the fractured skeleton. FIG. 1A shows a transverse stable fracture. Such fracture only needs a suitable pressure exerted onto the fractured skeleton to fix the fractured skeleton. Thereafter, the fractured skeleton will stably adjoin without deformation. This is the optimal fixing condition. FIGS. 1B and 1C show oblique fractures which are not stable. After pressurized and fixed, as shown in FIG. 1D, the component force will make the skeleton obliquely displace. Excessively large displacement will torque the fractured skeleton and lower the fixing and pressurizing effect. Therefore, left or right displacement will take place and it is impossible to stably pressurize and fix the fractured skeleton. Moreover, the main body 3 of the conventional in-marrow nail is not designed with thread pressurizing structure or the polished section 33 free from the thread of the in-marrow nail is very short. Therefore, it often takes place that when nailed into the fractured skeleton, the polished section can be hardly accurately aligned with the fractured portion and is very close to the adjoining section of the thread section and the polished section where the stress is concentrated. In addition, the diameter of the thread section is smaller than the diameter of the polished section 33. Therefore, in clinic use, breakage of the nail often takes place due to insufficient strength. The breakage is easiest to take place at the position near the adjoining section of the thread section and the polished section where the stress is concentrated. As a result, the broken nail will remain in the marrow and can be hardly taken out. In addition, with respect to fracture of clavicle trunk, the in-marrow nail is nailed into the fractured skeleton after the skeleton is restored. By way of the analysis in material dynamics, the middle of the transverse rod mainly suffers a bending force. The magnitude and direction of the force are as shown in FIG. 6. Two ends of the nail are inserted into the dense section of the clavicle and deemed as an integral body with the clavicle. The force application condition is as that two ends of the nail are tightly pinched by the thumbs and index-fingers of both hands. When suffering force, two ends are forced downward, while the middle is forced upward. Therefore, in the case that the effective length of the middle polished section is properly elongated, it is avoided that the section suffering greater stress is just positioned at the weaker section of the nail. This lowers the possibility of breakage of the nail.
It is therefore a primary object of the present invention to provide an improved in-marrow nail structure including an in-marrow nail main body two ends of which are respectively disposed with a thread tip section and a thread tail section. A polished section is formed between the two ends. The diameters of the thread tip section and the thread tail section of the main body are both larger than the diameter of the polished section and the effective length of the polished section is elongated so that the stress is evenly shared by respective portion of the main body during pressurizing. Therefore, the breakage due to the concentrated stress taking place on the adjoining sections of the thread section and the polished section of the main body can be avoided and a more firmly restoring and fixing effect is provided for the fractured skeleton.
It is a further object of the present invention to provide the above in-marrow nail structure in which the diameter of the thread tip section of the main body is slightly larger than the diameter of the thread tail section. Therefore, the thread tip section can easily firmly thrust into the dense section of the proximal end of the fractured skeleton to reduce the displacement caused by pressurizing. In addition, the thread tip section can directly preliminarily thrust through the marrow without using any other tool so that the operation procedure is simplified and the operation time is shortened.
It is still a further object of the present invention to provide the above in-marrow nail structure in which the diameter of the thread tail section is slightly smaller than the diameter of the thread tip section, whereby when the nut is tightened to press the distal end of the fractured skeleton, the diameter of the thread tail section is smaller than the diameter of the hole drilled by the thread tip section and the distal fractured section is slided and pressed toward the proximal fractured section and tightly mated therewith.